Cabinets, bookcases and the like generally include a number of shelves supported between a pair of side walls. The shelves can be supported in either fixed or adjustable positions. Adjustability, of course, is desireable because it allows the user to vary spacing between the shelves in accordance with the height of the items stored thereon. This is typically accomplished with brackets or clips, two of which are generally provided at each end of each shelf, for insertion into holes or sockets in the side walls.
Various types of such shelf support brackets or clips have been available heretofore. In their simplest form, they comprise posts or pins which protrude outwardly from the side wall beneath the edge of the shelf. Such shelf supports provide no locking or retention of the shelves against upward or outward separation from the side walls.
Various forms of shelf supports or brackets having a locking or retention function have also been available heretofore. For example, U.S. Pat. No. 3,759,191 to Freeman shows a reversible cabinet shelf bracket which is rotatable 180.degree. between an up/locked position wherein a vertical pin on the end of a flange is received by a socket in the underside of the shelf, and a down/unlocked position wherein the pin is out of engagement with the shelf. This bracket retains the shelf against outward movement from the side walls, but not against upward movement or tipping.
Shelf supports with a vertical retention function have also been available heretofore. For example, U.S. Pat. No. 3,870,266 to MacDonald shows a self-locking shelf support comprising an L-shaped bracket with a retractable spring pin at the upper end thereof. U.S. Pat. Nos. 3,471,111 and 3,471,112 to MacDonald show shelf support brackets having resilient fingers which engage the top surface of the shelves. U.S. Pat. Nos. 4,666,117 to Taft; 4,432,523 to Follows; and 4,037,813 to Loui are also representive of the prior art in this regard. While these brackets constrain the shelves against vertical separation, they are only adapted for use with one shelf thickness.
A need has thus arisen for an improved shelf support bracket which can be used with either one of two predetermined thicknesses of shelves, while providing retention against both vertical and outward separation from the side walls.